Permanent Magnet Motors, Electronically Commutated Motors, Coreless, Ironless Core, Slotless, DC Brush, radial and linear electric motors and generators manufactured today typically use round magnet wire to produce the electrical current path within the electromotive coil winding. The circular shape of round magnet wire limits the amount of current carrying conductive copper that can be fit into a given volume. Motor designers strive to achieve conductor configurations that maximize the amount of copper in the magnetic field of the motor stator or armature to enhance motor performance. Motor coils with higher conductor packing-factor or slot-fill ratios exhibit better overall performance than coils with lower packing-factor or slot-fill ratios.
An electric motor coil construction for either armature or stator that maximizes the amount of conductors within the magnetic gap of the rotor decreases the electrical resistance of the circuit within the motor. As an electric motor armature and/or stator construction increases the amount of copper within the same space, electrical energy efficiency of the motor increases. Reduction of the coil electrical resistance (R) proportionally reduces the heat losses of the coil circuit due to the product of Current squared times electrical resistance. This lower resistance improves the amount of power that can be produced by a given electric motor.
Higher efficient use of energy is the result of this motor coil construction. The lowering of resistance in the coil and lowering of losses in the magnetic effects acting on the coil combine to enable a significant reduction of electrical usage in the resultant motor.
Motor coil construction and coil conductor shape impacts power losses in the coil called Eddy Current Losses resulting from a magnetic field sweeping the conductors. Eddy Current Losses are a function of the rate of change of the magnetic field. This loss is an exponential function of the frequency and limits the maximum speed of any motor.
A rectangular shaped electrical current conductor with the narrow dimension of the conductor presented to the rotating and oscillating magnetic field produced by the magnetic component of the motor will reduce the eddy current drag losses in the motor due to the exponential reduction of losses with a linear reduction in the width of the conductor facing the magnetic field. Reduction of Eddy Current Losses will additionally improve the electrical efficiency of the motor and will allow higher motor speeds before eddy core loss limits motor speed.
A narrow rectangular conductor will enable an increased number of electrical turns in a given space. This will allow for motor designs with a wider range of operating motor voltages and speeds.
Electrical insulation is used to coat magnet wire; many suitable choices are readily available. This insulation is required to protect the electrical circuit from high voltage breakdown. Wire coatings applied in the production of magnet wire have high insulating performance whereas the use of bare copper conductor construction requires very complete post construction addition of insulation encapsulation to reduce the risk of high voltage breakdown capability.
Traditional motors use round wire electric current conductors to fill the space allowed for the production of inductive coils. Round wire will fill only 55% of the space available with copper. Rectangular wire construction can be nested to better fill the space and achieve up to 85% fill of the available magnetic field space with copper. Higher conductor fill ratios or higher copper packing factor increases the power capability of the resulting motor.
Round wire can be bent into a radius to allow construction of a coil with each two end turns and each complete turn of wire will create one side of the turn traversing up and one side traversing down. This creates excessive length in the end-turn thereby increasing the electrical resistance of the coil. Making a shortened end turn will decrease the resistance of the circuit relative to round wire construction. End turns of continuous wound coil construction increases the overall length of the wire for each turn of the coil therefore increasing the overall electrical resistance of the coil. An end turn construction with a mechanically bonded joint reduces the length for each turn in the coil assembly reducing the overall length of the coil, reducing weight and reducing electrical resistance.